The present application relates to the field of radiographic imaging. It finds particular application with the provision of electrical power for computed tomography (CT) scanners, a line scanner, or other radiography imaging system (e.g., mammography system, general radiology system, etc).
Radiographic imaging systems, such as computed tomography (CT) systems, line scanners, etc., provide information, or images, of an object under examination (e.g., interior aspects of an object under examination). Generally, the object is exposed to radiation, and one or more images are formed based upon the radiation absorbed by the object, or rather an amount of radiation that is able to pass through the object. Typically, highly dense objects absorb (e.g., attenuate) more radiation than less dense objects, and thus an object having a higher density, such as a bone or gun, for example, will be apparent when surrounded by less dense objects, such as fatty tissue or clothing, for example. A detector array, generally positioned opposite a radiation source from which radiation is emitted relative the object under examination, is configured to detect radiation that traverses the object under examination and convert such radiation into signals and/or data that may be processed to produce the image(s). Such an image(s) may be viewed by security personnel to detect threat items (e.g., weapons, etc.) and/or viewed by medical personnel to detect medical condition (e.g., cancerous tissue).
In some scanners, such as three-dimensional imaging scanners (e.g., CT scanners), for example, the detector array and radiation source are mounted on opposing sides of a rotating gantry that forms a ring, or donut, around the object under examination. In such a scanner, the rotating gantry (including the radiation source and/or detector array) is rotated in a circle situated within an x, y plane about an axis extending in the z-dimension (e.g., an “isocenter”) during an examination. The object is generally supported by a support article (e.g., a bed, conveyor belt, etc.) that runs in the z-direction substantially parallel to the mechanical center of rotation (e.g., the isocenter). As the rotating gantry is rotated, radiation is substantially continuously emitted from a focal spot of the radiation source toward the object under examination.
Medical CT systems typically utilize a large amount of power for a short period of time (periodic duty cycle), unlike security-based CT systems, which typically utilize less power relatively continuously. A medical CT scanner typically utilizes a large amount of power while the X-ray tube is on, for example, from 30 to 100 kW for a scan. This amount of electrical power cannot be provided by the standard single phase mains power receptacle, which typically provides up to four kW of service.
Traditionally, this high power, periodic duty cycle requirement calls for using a three-phase power line installation that is capable of providing the power continuously even though it is merely used in bursts. A dedicated, three-phase power connection is often made to satisfy the momentary demand, thereby requiring a special connection, and availability of three-phase service. However, some parts of the world cannot meet the power line stability required and special power regulators must be installed, such as for the three-phase service. This type of siting requirement can be expensive, may be limited, and can deny CT technology in smaller settings. Further, if the CT apparatus is connected to a dedicated line its portability is limited.
However the duty cycle of a CT scanner is low (periodic), particularly in a medical-type operation. For example, for medical CT scanning, a patient is typically brought into a room where the scan is performed, and then another patient is brought in, where a period of time elapses between scans. Therefore, even though the energy requirements for a medical-type CT scan are high, the duty cycle is low and intermittent, providing a time between uses where energy could be stored for use during a scan. Previously, battery systems were installed on the rotating gantry side of the CT apparatus. However, this arrangement limited the choice of batteries, limited power capabilities, and required the whole power chain to rotate. This made for a lot of weight to be accommodated and balanced on the rotating side, making the CT machines costly and difficult to set up.